1. Field of the Invention
The present invention relates to a method of manufacturing an electro-optical apparatus substrate that sequentially has a light shield layer of a predetermined pattern, an insulation layer and a transistor element on a surface of an optically transparent substrate, an electro-optical apparatus substrate which is manufactured by the manufacturing method, an electro-optical apparatus having the electro-optical apparatus substrate, and an electronic apparatus.
2. Description of the Related Art
An SOI (Silicon On Insulator) technique for forming a single crystal silicon thin film on an insulating substrate and then forming a semiconductor device of the single crystal silicon thin film has the merits of making a speed of an element faster, making a consumption power lower and making an integration degree higher. Thus, it is preferably used in an electro-optical apparatus, for example, such as a liquid crystal device and the like.
When the SOI technique is applied to the electro-optical apparatus as mentioned above, a single crystal silicon layer of a thin film is formed by laminating a single crystal silicon substrate on an optically transparent substrate and then polishing it. So, a transistor element, for example, such as MOSFET for driving a liquid crystal or the like, is constituted by the single crystal silicon layer.
By the way, in a projection display, for example, such as a projector using a liquid crystal device or the like, a light is inputted from the side of the optically transparent substrate (i.e., one surface of the liquid crystal device) which is one of the two substrates constituting the liquid crystal device. In order to prevent a light leak current from being generated as this light is inputted to a channel region of the transistor element formed on the surface of the other substrate, it is typically designed to form a light shield layer on the side of the transistor element, at which the light is inputted.
However, even if the light shield layer is formed on the side of the transistor element at which the light is inputted, when the substrate on which the transistor element is formed has the optically transparent property, the light inputted to the liquid crystal device may be reflected on a boundary face of a rear of the substrate on which the transistor element is formed, and may be inputted to the channel portion of the transistor element as a return light. This return light is little as a rate with respect to an amount of the lights inputted from the surface of the liquid crystal device. However, there may be the considerable possibility that the light leak current is generated in an apparatus using a very strong light source such as a projector or the like. That is, the return light from the rear of the substrate on which the transistor element is formed has an influence on a switching property of the element, and causes the performance of the element to be deteriorated. By the way, here, let us suppose that the plane on which the single crystal silicon layer is formed is referred to as the surface of the substrate, and the opposite side is referred to as the rear.
Japanese Laid Open Patent Application (JP-A-Heisei, 10-293320) proposes a technique for forming a light shield layer on a surface of a substrate on which transistor elements are formed, correspondingly to each transistor element. This proposes a method of forming the light shield layer of a predetermined pattern on the substrate surface, and forming an insulation layer on the light shield layer, and then polishing and smoothing a surface of the insulation layer and laminating or bonding a single crystal silicon substrate on the polished surface.
However, in the typical electro-optical apparatus, the transistor elements are formed only in a display region (pixel portion) on the surface of the substrate, and the transistor elements are not formed in a non-display region. In this way, there are the region in which the transistor elements are crowded (the formation region) and the non-crowded region (the non-formation region) in which the transistor elements are not crowded. For this reason, each piece of light shield layers disposed correspondingly to the respective transistor elements are distributed at the similar density. As a result, concave and convex portions are formed on a surface of the insulation layer formed on the light shield layers, and a certain distribution is also induced in those concave and convex portions. Thus, even if the surface of the insulation layer is polished, the variation in the polished degree is induced on the surface of the substrate. So, even if the entire surface of the substrate is polished, the insulation layer becomes relatively thick in the portion where the convex portions are crowded, and the insulation layer becomes relatively thin in the portion where the convex portions are not crowded (i.e., the portion where the concave portions are crowded). Hence, this leads to the fear of the degradation in the smoothness or flatness on the surface of the insulation layer after the polishing operation.
For example, as shown in FIG. 19(a), assuming that a region 1010 where light shield layers 1003 are crowded and a region 1020 where the shield layers 1003 are not crowded exist on a surface of a substrate 1001, the number and the area of concave portions formed on the region 1020 where the light shield layers 1003 are not crowded are greater and wider than those of the region 1010 where the light shield layers 1003 are crowded, on a surface of an. insulation layer 1004 formed on the substrate 1001 on which the light shield layers 1003 have been formed. By the way, even in the region 1010 where the light shield layers 1003 are crowded, minute concave and convex portions are formed on the surface of the insulation layer 1004, depending on the patterns of the light shield layers 1003. However, they are omitted on FIG. 19(a), for the simplicity.
As mentioned above, if the surface of the insulation layer 1004 having the distribution in the concave and convex portions is polished, the region in which the area of the convex portions is narrower (i.e., the region 1020 where the light shield layers: 1003 are not crowded) is polished faster than the region in which the area of the convex portions is wider (i.e., the region 1010 where the light shield layers 1003 are crowded), on the surface of the insulation layer 1004. As a result, as shown in FIG. 19(b), the insulation layer 1004 in the region 1020 where the light shield layers 1003 are not crowded is excessively polished, which causes a stage difference between the region 1010 where the light shield layers 1003 are crowded and the region 1020 where they are not crowded, on the surface of the insulation layer 1004. Accordingly, the smoothness on the surface of the insulation layer 1004 is made lower.
As mentioned above, the drop in the smoothness on the surface of the insulation layer brings about the following problems. As the first problem, there may be the fear that a void is induced on the lamination boundary between the insulation layer and the single crystal silicon layer, and this causes the deterioration in the performance of the transistor element formed in the region where this void exists. As the second problem, there may be the fear that the strength of the lamination between the insulation layer and the single crystal silicon layer is reduced, which causes the defect of film strip and the like to be induced in the process of forming the transistor element after the formation of the single crystal silicon layer, and thereby results in the drop in a yield of a product.
In addition, even if the insulation layer surface can be smoothed or flattened, there is no method of detecting an ending point of polishing i.e., a moment when the insulation layer has been completely smoothed. Thus, the polishing process is controlled only by the polishing time duration. However, since the polishing rate is changed due to various factors such as a batch or lot of the used polishing liquid, a difference in the type of the polishing machined and the like, the time duration by which the insulation layer has been completely smoothed is also changed due to the actual polishing condition at that time. Accordingly, there may arise such a case that the surface of the insulation layer cannot be completely smoothed, even if polishing is conducted for a constant time duration.
The present invention is proposed in view of the above mentioned problems. It is therefore an object of the present invention to provide: a method of manufacturing an electro-optical apparatus substrate such that an insulation layer surface on which a single crystal silicon layer is laminated can be smoothed; the electro-optical apparatus substrate; an electro-optical apparatus having the electro-optical apparatus substrate; and an electronic apparatus having the electro-optical apparatus.
It is another object of the present invention to provide: a method of manufacturing an electro-optical apparatus substrate such that s surface of an optically transparent substrate on which a light shielding layer and an insulation layer are formed and on which a single crystal silicon layer is laminated can be smoothed, and that the ending point of polishing can be easily detected at the time of polishing the insulation layer; the electro-optical apparatus substrate; an electro-optical apparatus having the electro-optical apparatus substrate; and an electronic apparatus having the electro-optical apparatus.
The inventor of the present invention found out that, in a case that the area of the concave portions is relatively large on the surface of the optically transparent substrate such as a case that the light shield layer is formed only in the formation region of the transistor elements, it is possible to achieve the above mentioned object by the following method, so that the surface of the insulation layer on which the single crystal silicon layer is laminate can be smoothed.
Namely, the above object of the present invention can be achieved by a first method of manufacturing an electro-optical apparatus substrate, including the processes of: forming a light shield layer above one surface of an optically transparent substrate; patterning the light shield layer to thereby form a patterned light shield layer at least in a formation region of each transistor element to be formed; forming a first insulation layer above the one surface of the optically transparent substrate above which the patterned light shield layer has been formed; forming a second insulation layer having a polishing rate lower than that of the first insulation layer, on the first insulation layer; polishing a surface of the second insulation layer; laminating a single crystal silicon layer above the polished surface of the second insulation layer; and forming the each transistor element by using the single crystal silicon layer.
The inventor of the present invention found out that, in a case that the area of the concave portions is relatively large on the surface of the optically transparent substrate such as a case that the light shield layer is formed only in the formation region of the transistor elements, it is possible to smooth the surface of the insulation layer, by polishing the surface of the substrate after (i) forming the first insulation layer on the optically transparent substrate on which the patterned light shield layer has been formed and (ii) forming the second insulation layer whose polishing rate is lower than (i.e., which is polished slower than) the first insulation layer, by virtue of the existence of the second insulation layer to prevent the excessively polished portion from being generated. In addition, the reason why the surface of the insulation layer can be smoothed by this method will be explained in more detail in the embodiment section.
In one aspect of the first method of the present invention, the first insulation layer is partially exposed by the step of polishing the surface of the second insulation layer.
In this aspect, a height of an exposed surface of the first insulation layer with respect to the one surface of the optically transparent substrate may be same as that of the polished surface of the second insulation layer.
In another aspect of the first method of the present invention, at the step of patterning the light shield layer, the patterned light shield layer is formed only in the formation region of the each transistor element.
The inventor of the present invention also found out that, in a case that the area of the concave portions is relatively small on the surface of the optically transparent substrate such as a case that the light shield layer is formed also in the non-formation region of the transistor elements, it is possible to achieve the above mentioned object by the following method, so that the surface of the insulation layer on which the single crystal silicon layer is laminate can be smoothed.
Namely, the above object of the present invention can be also achieved by a second method of manufacturing an electro-optical apparatus substrate, including the processes of: forming a light shield layer above one surface of an optically transparent substrate; patterning the light shield layer to thereby form a patterned light shield layer at least in a formation region of each transistor element to be formed; forming a first insulation layer above the one surface of the optically transparent substrate above which the patterned light shield layer has been formed; forming a second insulation layer having a polishing rate lower than that of the first insulation layer, on the first insulation layer; forming a third insulation layer having a polishing rate higher than that of the second insulation layer, on the second insulation layer; polishing a surface of the third insulation layer; laminating a single crystal silicon layer above the polished surface of the third insulation layer; and forming the each transistor element by using the single crystal silicon layer.
The inventor of the present invention found out that, in a case that the area of the concave portions is relatively small on the surface of the optically transparent substrate such as a case that the light shield layer is formed also in the non-formation region of the transistor elements, it is possible to smooth the surface of the insulation layer, by polishing the surface of the substrate after (i) forming the first insulation layer on the optically transparent substrate on which the patterned light shield layer has been formed (ii) forming the second insulation layer whose polishing rate is lower than (i.e., which is polished slower than) the first insulation layer, and (iii) forming the third insulation layer whose polishing rate is higher than (i.e., which is polished faster than) the second insulation layer, by virtue of the existence of the second insulation layer to prevent the excessively polished portion from being generated. In addition, the reason why the surface of the insulation layer can be smoothed by this method will be explained in more detail in the embodiment section.
In one aspect of the second method of the present invention, the second insulation layer is partially exposed by the step of polishing the surface of the third insulation layer.
In this aspect, a height of an exposed surface of the second insulation layer with respect to the one surface of the optically transparent substrate may be same as that of the polished surface of the third insulation layer.
In another aspect of the second method of the present invention, at the step of patterning the light shield layer, the patterned light shield layer is formed in a non-formation region of the each transistor element where the each transistor element is not formed.
The above object of the present invention can be also achieved by a third method of manufacturing an electro-optical apparatus substrate, including the processes of: forming a light shield layer above one surface of an optically transparent substrate; patterning the light shield layer to thereby form a patterned light shield layer at least in a formation region of each transistor element to be formed; forming an insulation layer on the one surface of the optically transparent substrate on which the patterned light shield layer has been formed; polishing a surface of the insulation layer until a surface of the patterned light shield layer is exposed; laminating a single crystal silicon layer above the polished surface of the insulation layer and the exposed surface of the patterned light shield layer; and forming the each transistor element by using the single crystal silicon layer.
The present inventor found out that, by forming the insulation layer on the optically transparent substrate on which the light shield layer has been formed and then polishing the surface until the light shield layer is exposed in this manner, it is possible to smooth the surface of the optically transparent substrate onto which the single crystal silicon layer is laminated, and it is also possible to easily detect the stopping point of polishing by giving the polishing stopper function to the light shield layer, by using the fact that the materials of the light shield layer and the insulation layer are different from each other.
For example, in case of using the CMP method, since the light shield layer comprising metal etc., does not chemically react with the polishing liquid, at the moment when the surface of the light shield layer is exposed, the friction force between the polishing pad for polishing the optically transparent substrate and the optically transparent substrate is certainly dropped. Also, the vibration of the substrate holder for holding the optically transparent substrate is certainly changed. Therefore, by detecting the friction force between the polishing pad and the optically transparent substrate or the vibration of the substrate holder, it is possible to easily detect the stopping point of polishing.
In the present application, xe2x80x9cthe light shield layer has a polishing stopper functionxe2x80x9d means that xe2x80x9cthe stopping point of polishing is detected by detecting the moment when the surface of the light shield layer is exposedxe2x80x9d as described above.
Also, sine the oxide film is formed in advance on the surface of the single crystal silicon substrate used for lamination at its side of lamination, it is possible to prevent the pollution from the light shield layer to the transistor element, even if the formation of the transistor element is performed after laminating the single crystal silicon substrate directly onto the surface of the light shield layer comprising metal etc., and then make this single crystal silicon substrate thinner to be the single crystal silicon layer.
However, even in a case that the oxide film is formed on the surface of the single crystal silicon substrate, if this surface oxide film is very thin or the like so that there is a possibility of the pollution from the light shield layer to the transistor element, it is desirable to form an insulation layer on the surface of the light shield layer, before laminating the single crystal silicon substrate. In such a case, the following fourth method is desirable.
Namely, the above object of the present invention can be also achieved by a fourth method of manufacturing an electro-optical apparatus substrate, including the processes of: forming a light shield layer above one surface of an optically transparent substrate; patterning the light shield layer to thereby form a patterned light shield layer at least in a formation region of each transistor element to be formed; forming a first insulation layer on the one surface of the optically transparent substrate on which the patterned light shield layer has been formed; polishing a surface of the first insulation layer until a surface of the patterned light shield layer is exposed; forming a second insulation layer above the polished surface of the first insulation layer; laminating a single crystal silicon layer above the second insulation layer; and forming the each transistor element by using the single crystal silicon layer.
According to the fourth method of the present invention, by forming the first insulation layer on the optically transparent substrate on which the light shield layer has been formed, and by polishing the surface of the optically transparent substrate on which the first insulation layer has been formed until the surface of the light shield layer is exposed, the surfaces of the first insulation layer and the light shield layer are smoothed. After that, by forming the second insulation layer, since the surface of the second insulation layer is smoothed, it is possible to smooth the surface of the optically transparent substrate onto which the single crystal silicon layer is laminated. Further in this case, since the second insulation layer is formed between the light shield layer and the transistor element, it is possible to almost perfectly prevent the pollution from the light shield layer to the transistor element.
According to the above described first to fourth methods of the present invention, since the surface of the insulation layer can be smoothed, there is no or little void on the lamination boundary between the insulation layer, so that it is possible to prevent the property of the transistor element form being deteriorated. Further, since the lamination strength between the insulation layer and the single crystal silicon layer is strong, it is possible to prevent a defect such as a film strip or the like from being induced in the process of forming the transistor element, so that the yield can be improved.
The above object of the present invention can be also achieved by a first electro-optical apparatus substrate provided with a patterned light shield layer having a predetermined pattern, an insulation film and a transistor, which are sequentially formed above one surface of an optically transparent substrate, the insulation film comprising (i) a first insulation layer and (ii) a second insulation layer, which is partially formed on the first insulation layer and whose polishing rate is lower than that of the first insulation layer, so that a surface of the insulation film is smoothed, the transistor element having a semiconductor layer comprising a single crystal silicon layer.
According to the first electro-optical apparatus substrate of the present invention, which can be manufactured by the above described first method of the present invention, there is no or little void on the lamination boundary between the insulation layer and the single crystal silicon layer, the lamination strength between the insulation layer and the single crystal silicon layer is strong, the variation and the defect are hardly induced in the property of the transistor element.
In one aspect of the first electro-optical apparatus substrate of the present invention, the patterned light shield layer is formed only in an formation region of the transistor element.
In another aspect of the first electro-optical apparatus substrate of the present invention, the first insulation layer comprises silicon oxide, and the second insulation layer comprises silicon nitride.
The above object of the present invention can be also achieved by a second electro-optical apparatus substrate provided with a patterned light shield layer having a predetermined pattern, an insulation film and a transistor, which are sequentially formed above one surface of an optically transparent substrate, the insulation film comprising (i) a first insulation layer, (ii) a second insulation layer, which is formed on the first insulation layer and whose polishing rate is lower than that of the first insulation layer, and (iii) a third insulation layer, which is partially formed on the second insulation layer and whose polishing rate is higher than that of the second insulation layer, so that a surface of the insulation film is smoothed, the transistor element having a semiconductor layer comprising a single crystal silicon layer.
According to the second electro-optical apparatus substrate of the present invention, which can be manufactured by the above described second method of the present invention, there is no or little void on the lamination boundary between the insulation layer and the single crystal silicon layer, the lamination strength between the insulation layer and the single crystal silicon layer is strong, the variation and the defect are hardly induced in the property of the transistor element.
In one aspect of the second electro-optical apparatus substrate of the present invention, the patterned light shield layer is formed in a non-formation region of the each transistor element where the each transistor element is not formed.
In another aspect of the second electro-optical apparatus substrate of the present invention, the first insulation layer and the third insulation layer comprise silicon oxide, and the second insulation layer comprises silicon nitride.
The above object of the present invention can be also achieved by a third electro-optical apparatus substrate provided with: a patterned light shield layer having a predetermined pattern above one surface of an optically transparent substrate; an insulation layer which is formed above the one surface of the optically transparent substrate at an area where the patterned light shield layer is not formed, which has a thickness same as that of the patterned light shield layer, and whose surface is smoothed; a transistor element, which is formed above the patterned light shield layer and has a semiconductor layer comprising a single crystal silicon layer.
According to the third electro-optical apparatus substrate of the present invention, which can be manufactured by the above described third or fourth method of the present invention, there is no or little void on the lamination boundary between the insulation layer and the single crystal silicon layer, the lamination strength between the insulation layer and the single crystal silicon layer is strong, the variation and the defect are hardly induced in the property of the transistor element.
In one aspect of the third electro-optical apparatus substrate of the present invention, the insulation layer is formed by polishing a surface of an insulation film formed on the one surface of the optically transparent substrate on which the patterned light shield layer has been formed, the patterned light shield layer functioning as a stopper for polishing in a process of polishing the insulation film.
In another aspect of the third electro-optical apparatus substrate of the present invention, on the surfaces of the patterned light shield layer and the insulation layer, a second insulation layer is formed, the transistor element being disposed on a surface of the second insulation layer.
The above object of the present invention can be also achieved by an electro-optical apparatus provided with: (A) any one of the above described first, second and third electro-optical apparatus substrate of the present invention; (B) another optically transparent substrate disposed to be opposed to the one surface of the optically transparent substrate of the electro-optical apparatus substrate; and (C) an electro-optical material layer sandwiched between the two optically transparent substrates.
According to the electro-optical apparatus of the present invention, since it is provided with the electro-optical apparatus substrate according to the present invention, it is possible to provide the electro-optical apparatus, such as an LCD or the like, having the excellent performance.
The above object of the present invention can be also achieved by an electronic apparatus provided with the above described electro-optical apparatus of the present invention.
According to the electronic apparatus of the present invention, since it is provided with the electro-optical apparatus according to the present invention, it is possible to provide the electronic apparatus, such as a projector or the like, having the excellent performance.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.